This application is based upon and claims the benefit of priority of Japanese Patent Applications No. 2000-209785 filed on Jul. 11, 2000 and No. 2001-78103 filed on Mar. 19, 2001, the contents of which are incorporated herein by reference.
1. Field of the Invention
The present invention relates to an intake manifold having an intake passage made of resin and metal.
2. Description of Related Art
It is known to make an entire body of an intake manifold from metal to improve heat resistance and strength for joining with an engine. However, an intake manifold formed of metal is heavy in weight and has a higher manufacturing cost.
It is also known to provide an intake manifold applied to a V-type engine with metal distribution pipes arranged on a bank of the engine and a resin intake air introduction pipe arranged on a side opposite to the engine with respect to the distribution pipes.
According to the conventional intake manifold having the resin intake air introduction pipe, noises due to the following are emitted through the resin pipe;
(a) pressure pulsation of intake air on opening and closing intake valves,
(b) throttle noises generated by a valve member of a throttle device that rotates rapidly to change from a closing state to an opening state on quick engine starting, and
(c) airflow noises of intake air flowing in the intake manifold.
When the pressure pulsation, the throttle noises and the airflow noises as mentioned above are transmitted to the resin intake air introduction pipe of the intake manifold, which is arranged on the side opposite to the engine with respect to the metal distribution pipes and whose resilience is smaller than the metal pipe, the noises are emitted to the outside through the resin pipe.
An object of the invention is to provide an intake manifold in which emitting noises are limited without increasing the weight and the manufacturing cost.
To achieve the above objects, the intake manifold is composed of a resin member and a metal member. The metal member is combined with and holds the resin member so as to overlap the resin member on a side opposite to the engine so that the resin member and the metal member constitute an intake passage through which intake air is supplied from a throttle device to each cylinder of the engine. The metal member is provided with fittings for mounting the intake manifold on the engine.
With the intake manifold mentioned above, even if the pressure pulsation, the throttle noises and the airflow noises are transmitted to the resign portion, the metal portion shields the noise emitted from the resin portion so that the noises are prevented from being given out to the outside since the metal portion overlaps the resin portion on a side opposite to the engine. The intake manifold mentioned above has a noise shield effect similar to that of the conventional all metal intake manifold and, further, is lighter in weight and manufactured at less cost, compared with the conventional all metal intake manifold.
In a case of classifying the intake passage into an intake air introduction passage connectable to the throttle device and a plurality of intake air distribution passages, one end of each of which is connectable via the fittings to each of the cylinders of the engine and the other end of each of which communicates with the intake air introduction passage, it is preferable that the resin member mainly constitutes the intake air introduction passage and the metal member mainly constitutes the intake air distribution passages.
Further, it is preferable in view of lighter weight and lower cost that the metal member is made of aluminum.